- Participants will have five rTMS sessions, one per day for 5 days in a row. Each session will last 1 to 2 hours. Participants will have either real or sham (simulated) rTMS while looking at pictures that may or may not be related to cocaine use, and will also perform a simple decision task that is the same as the one given during the MRI scans. The decision as to whether participants get real or sham rTMS will be made by chance. Neither the participants nor the investigators will know which type the participants are getting. - Participants will have two follow-up visits one and two weeks after their last rTMS session. At each visit they will be checked for cocaine and other substance use and for possible side-effects from rTMS.